An in-cylinder pressure detection device in which a projection is provided on a reverse face of a metal diaphragm provided at the extremity of an in-cylinder pressure sensor facing a combustion chamber of an internal combustion engine, and a load due to deformation of the metal diaphragm is transmitted to a pressure detection element via the projection is known from Patent Document 1 below.
Furthermore, an in-cylinder pressure detection device in which a piezoelectric element is provided on an inner wall face of a cylinder head facing a combustion chamber of an internal combustion engine, at the extremity of a glow plug or a spark plug facing the combustion chamber, or at the extremity of an injector facing the combustion chamber, and an in-cylinder pressure is detected based on a voltage generated due to deformation of the piezoelectric element is known from Patent Document 2 below.